1. Field of the Invention
The present invention relates to a tracking method, and more particularly to a method for tracking a pollution source in process water.
2. Related Art
Semiconductor, thin film transistor liquid crystal display (TFT-LCD), and other high-tech industries have become major industries in Taiwan. In the high-tech industries, after each process is completed, pure water or ultra-pure water is used for a great amount of rinsing steps, so as to ensure the stability of the next process, resulting in high water consumption in the high-tech industries. Secondly, since it is difficult to obtain water sources and develop water resources due to the special geographic environment of Taiwan, and the requirement for the reclaim rate of process water regulated in decrees becomes increasingly strict, it is one of important tasks in the high-tech industries of Taiwan to improve the reclaim rate of process water when water resources are limited, so as to reduce the waste of the water resources, thereby achieving water saving and environmental protection policy.
Moreover, if people attach importance to the improvement of the reclaim rate of the process water, but neglect the water quality of the reclaimed water, the application of the reclaimed water will be greatly limited, and even the quality of the ultra-pure water supply will be polluted, thereby reducing the production capacity. That is to say, the stability of the water quality of the reclaimed water has great effects. Therefore, it is a problem to be urgently overcome by persons skilled in the art to compromise the improvement of the reclaim rate of the process water and the water quality of the reclaimed water.
Rinsing water of a semiconductor wafer factory is taken as an example. Drain water from rinsing tanks for rinsing wafers is respectively drained through drains of the different tanks, gathered to a sub-main drain and a main drain in sequence, and then is drained to an intermediate tank (or called a buffer tank). In practice, the water quality (for example, conductivity, total organic carbon (TOC), pH value, and the like) of the drain water drained from each rinsing tank is not monitored during the draining process, but is monitored after the drain water is drained to the buffer tank. At this time, if the water quality of the rinsing drain water measured in the buffer tank satisfies an allowable standard value set by a reclaiming system, the rinsing drain water is drained to a process-water reclaiming system, that is, an ultra-pure water front end, for reclamation. However, once the water quality of the rinsing drain water measured in the buffer tank exceeds the allowable standard value set by the reclaiming system, in consideration of the yield, the water in the whole tank is guided to a waste water treatment system, and will not be reclaimed.
Briefly, when it is detected that the water in the buffer tank is seriously polluted, the water in the whole tank is directly drained to the waste water treatment system. As a result, a great amount of water is wasted. Moreover, since the drain water is drained to the buffer tank after being gathered through the drains of different sizes, and the water quality is monitored after the drain water is drained to the buffer tank, even if it is monitored that the water quality in the buffer tank exceeds the predetermined allowable standard value, it is impossible to know which rinsing tank the pollution source comes from. Therefore, it is a problem to be urgently overcome by persons skilled in the art to compromise the reclaim rate of the drain water and the stability of the water quality of the reclaimed water.